New demodulation scheme for laser-scanned acoustical-imaging systems

Abstract

Several acousto-optical imaging systems are described in the literature where the image information is obtained by scanning a focused beam over a flexible mirror located at the acoustical image plane. The small dynamic deformation of the mirror induces a shallow phase modulation in the scanning beam. This paper describes a time-delay filter that transforms the phase-modulated beam into an amplitude-modulated beam and compares the proposed method with other demodulation schemes described in the literature. Specifically, stability, resolution, sensitivity, and frequency responses are considered.